1. Field of the Invention
The present invention relates to an infrared reflecting laminated glass for an automobile which has excellent characteristics.
2. Description of the Prior Art
It has been known to use an infrared reflecting glass which reflects infrared solar rays thereby preventing a temperature rise in a room or decreasing the energy load for cooling a room. It has been known that such infrared reflecting glass is formed by coating a metal layer made of gold, silver, copper or aluminum on a surface of a glass sheet or coating a metal oxide layer made of cobalt oxide, iron oxide, chromium oxide, titanium oxide or tin oxide on a surface of a glass sheet. It has been considered that such infrared reflecting glass is not suitable for an automobile because of low percent of visible ray transmission or high percent of visible ray reflectivity. It is possible to provide a thin metal layer or metal oxide layer for increasing the visible ray percent transmission. However, this has a disadvantage, viz a satisfactory infrared reflecting characteristic is not obtained for a front glass of an automobile because more than 70% of visible ray transmission is required by regulation. It is optimum to have less than 12% of visible ray transmission and less than 65% of solar ray transmission and to have the capacity for intercepting ultraviolet rays having a wavelength of 3900 A or less. It has been difficult to obtain an infrared reflecting laminated glass which has satisfactory characteristics. There is no regulation for the visible ray percent reflectivity and the solar ray percent transmission. According to various experiments performed by the inventors, when the visible ray percent reflectivity is more than 12%, the visible ray percent transmission is too low for the glass to serve as an infrared reflecting glass for an automobile. Moreover, a reflected image adversely affects persons around the automobile. When the solar rays percent transmission is more than 65%, a satisfactory effect for preventing heat in a compartment of the automobile can not be expected. A deterioration of interiors in a compartment of the automobile by ultraviolet rays can be prevented by intercepting ultraviolet rays having a wavelength less than 3900 A etc.
The inventors have proposed an infrared reflecting laminated glass which is prepared by producing an infrared reflecting plastic film formed by sequentially coating a tungsten oxide layer having a thickness of 180 A to 500 A or 1400 A to 1600 A, a silver layer having a thickness of 80 A to 150 A and a tungsten oxide layer having a thickness of 180 A to 500 A or 1400 A to 1600 A on a plastic film, with said infrared reflecting plastic film held between a pair of polyvinyl butyral interlayer films the outer surface of which each has a glass sheet laminated thereto. According to various tests for durabilities of the infrared reflecting laminated glass, the effect for absorbing ultraviolet rays is not enough, and the infrared reflecting plastic film is disadvantageously colored.